There is a laundry list of symptoms associated with both hypothyroidism (underactive) and hyperthyroidism (overactive). However, Elizabeth Lee Vliet, MD, an internist in Dallas and author of Screaming to be Heard: Hormone Connections Women Suspect, and Doctors Still Ignore and Women, Weight and Hormones, says none of this is as clear cut as many doctors think. For one thing, she says, the thyroid regulates every cell in the body, including the ovarian hormones, and the secondary effects of an imbalance in these hormones can exacerbate problems with the hormones secreted by the thyroid.

What Goes Wrong

Perhaps for this reason, women are five to seven times more likely than men to experience thyroid problems. As many as 10% develop a thyroid problem after giving birth. The most common single disorder is an autoimmune problem (in which the body "fights" itself) called Hashimoto's disease, which results in underactive thyroid. Women with other autoimmune disorders are at prime risk for some form of thyroid dysfunction. "There is also evidence," Vliet says, "that pollutants such as PCBs and dioxin can damage the thyroid gland [in the womb]." Other culprits are radiation to the neck area and certain medications.